Pulse selector unit



June 15, 19.48. M, E, SALLACH 2,443,198

PULSE SELECTOR UNIT Filed Sept. 6, 1946 Z-ShQetS-Sheet 1 )te/465e nena/7354 l I fle-Maze meca/ffii f (il Y l l l l I l 0 |00 200 300 40D 500 ou M/ea .ffm/vas IN V EN TOR.

Jlme 15, 194,8. M E SALLACH 2,443,198

PULSE SELECTOR UNIT Filed Sept. 6. 1946 2 Sheets-Sheet 2 Y INVENTOR. my f: WM5/,f

Patented June l5, 1948 UNITED STATES PATENT OFFICE PULSE SELECTOR UNI'I.`

Max E. Sallach, Dayton, Ohio Application September 6, 1946, Serial No. 695.068

2 Claims. (Cl. 177-353) (Granted under the act of March 3, 1883, as

amended April 30, 1928,; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

This invention relates to a decoding circuit for use in systems of radio control, such as, for examplethe systems used in connection with radio controlled aircraft or guided missiles. It is the object of the invention to provide a decoder capable of analyzing a coded signal of the type containing a synchronizing pulse and one or more control pulses occurring at predetermined times after the synchronizing pulse, and causing corresponding control functions to' be performed.

In the drawings:

Fig. 1 is a block diagram of a typical system in which the decoder may be used;

Fig. 2 shows a number of wave forms obtained in the circuit of the decoder; and

Fig. 3 is a schematic diagram of the decoder circuit.

Referring to Fig. 1, the control system consists of a guiding means and a guided means, the guiding means comprising a radar transmitter I which transmits a series of pulses to the receiver 2 of the guided means. The output of this receiver is used to trigger transmitter 3 of the guided means, which transmits pulses back to receiver 4 in the guiding means. The output of receiver 4 isapplied to the indicator 5 to give information about the position and motion of the guided means. The encoder 6 is triggered by a pulse synchronized with the transmitted pulses ,of the radar transmitter and generates a coded signal consisting of one or more coded pulses occurring at predetermined times after the initial triggering pulses. The` number of control pulses present in the signal and the time at which they occur is controlled by stick I2 of control box. 1. The encoded signal is applied to transmitter 8 of the guiding means which transmits the signal to the receiver 9 of the guided means. The coded output signal of receiver 9 is applied to the decoder I which analyzes the signal and causes the control system Il to produce the desired changes in the motion 'of the guided means.

Reference is made to Fig. 3 for a description of the manner in which the decoder I0 of Fig, 1 analyzes the coded'signal and causes the desired control circuits to operate. The form of the coded signal is shown in Fig. 2(a) and consists of a synchronizing pulse followed by one or more control pulses, each corresponding to a particular control function that it is desired to produce in the guided means. The particular circuit described is designed to work with a signal consisting of any combination of'six control pulses occurring at multiples of microseconds but not exceeding 600 microseconds after the synchronizing pulse. The signal shown in Fig. 2(a)l comprises three control pulses occurring at 200, 300 and 500 microsecond intervals after the synchronizing pulse. The coded signal (obtained from transmission line 20) is amplied by gated video ampliiier Vi and applied by means of transformer 2| to the control grid of the right hand section of tube V2, the output of which is applied to the control grid of the right hand section of V3 through condensers 22 and 23.

The tube Vs is part of a conventional one cycle multivibrator circuit 24 having a condition of stability in which the current in the right hand section is a maximum and that in the left hand section is cut oif. The application of a negative pulse to the grid of the right hand section causes a rapid transition to the condition in which the current in the left hand section is a maximum and the right section is cut off. This condition exists until the condenser 23 has discharged sufciently to permit the grid of the right hand section to rise to the cut off point, at which time the multivibrator rapidly reverts to the initial condition with the right hand section conducting and the left hand section cut off. This cycle of operation produces a negative pulse at the anode of the left hand section, the length of which is determined by the time constant of the discharge path of condenser 23, which in this particular case is adjusted to give a pulse having a length somewhat in excess of 650 microseconds. The negative pulse produced at the anode of the left hand section of V3 yis applied to the suppressor grid of V1 by means of condenser 25 and resistor 26, therefore.- after the synchronizing pulse of the coded signal has passed through stages V1 and V2 and triggered the multivibrator circuit 24, the negative pulse produced by the multivibrator and applied to the suppressor grid of V1 renders this tube inoperative for the duration of the pulse and therefore does not permit V1 to pass any of the control pulses of the coded signal.

The negative pulse produced by the multivibrator 24 is also applied to the left hand section of V4 which acts as a keying amplier. This amplifier converts the pulse into a positive pulse which is applied to the anode of the left hand section of Vs and to the grid of the right hand section of Vs. The dual-triode Vs is part of an oscillator 21 which is a form of multivibrator having its frequency stabilized by the resonant circuit com-'- prising-conductance 28' and condensers 29 and 30. The oscillatoris `adjusted to afrequency of 10,000 cyclesper second and, since the keying pulse applied thereto has` a length in excess of 650 microseconds as stated above, the oscillator produces 6% complete cycles during the time it is keyed by the pulse. The output Wave of this oscillator is shown in Fig. 2(1)) and is developed across the primary winding of transformer 3|. This transformer is a diilerentiating device which produces across its secondary winding a voltage proportional to the rate of change of the voltage applied to the primary winding and therefore converts the output of the oscillator into a series of pulses of alternate polarity and spaced at 50 microsecond intervals as shown in Fig. 2(0) This series of pulses is applied to the grid of the right hand section of tube V4 which is biased to cutoff by means of the potential drop across rey sistor 32. When so biased, the tube will not pass negative pulses applied to its grid, however, positive pulses applied to the grid appear amplied and inverted in polarity in the output circuit. The output circuit oi this section of V4 therefore contains a series of negative pulses, as shown in Fig. 2(d), spaced at 100 microsecond intervals and starting 50 microseconds after the occurrence of the original synchronizing pulse.

Circuits 33 through 39 form a cascaded arrangement oftrigger circuits, each of which is of the Eccles-Jordan type. Referring to circuit 33, ,for example, the circuit comprises a dual-triode tube Vs in which the anode of each section is coupled to the grid of the other section. This type of circuit has two conditions of stability which are the condition in which the currentvin the left hand section is a maximum and that in the right hand section is zero, and the condition in which the current is the right hand section is a maximum and that in the left hand section is zero. Due to the regenerative action of a circuit of this type, any external inuence tending to change the circuit from one condition of stability will cause the change to progress in the same direction until the other condition of stability is reached. In the initial condition of operation of the decoder circuit, the left hand section of vVs is conducting and the -current inthe righthand section is zero. The synchronizingpulse of 4the coded signal after amplification by V1 and inversion by the left hand section of V2 is applied as a negative pulse to the control grid of the left hand section of Ve, causing the current in this section to be reduced and, as explained above, the circuit to be triggered to thevother condition of stability in which the current in the left hand section is zero and that inthe rightfhands'ection is a maximum. Fiftyfmlcrosecondsv later the `rst pulse of the series vof negative pulses'shown in Fig. 2(d) is applied to the control grid of the right hand section of Vs through condenser". This pulse reduces the current in the right hand section of Ve and causes the circuit to; be triggered back to its initial condition of stability'with kthe as initial tunesien nr-equilibrium.' in which the left hand section of V1 is conducting and the right hand. section cut off. to the other condition .of

' Aequilibrium in which the right hand section is left hand section'conducting andthe-right hand section cut off. This cycle of peration'ffproducesj a positive pulse 50v microseconds inilengthv at the anode of the left hand section ,of Vjasishown in Fig. 2(e). A negative triggerA 'pulsejis produced from the trailing edge of this pulse by means of conducting and the left hand section cut off. One hundred microseconds later the second negative pulse in the series shown in Fig. 2(d) is applied to the control grid of the right hand section of V1, thus causing the trigger circuit 34 to revert to its initial condition of stability in which the left hand section of Vv is conducting and the right hand section cut off. This cycle of operation produces at the anode of the left hand section a positive pulse of v100 microseconds duration as shown in Fig. 2(1') In a similar manner. the remaining circuits 35 through 39 produce successive 100 microsecond pulses as shown in Fig. 2(g) through (k), the last pulse in the series of Fig. 2(d) serving to trigger circuit 39 back to its original condition of stability in which the left hand section is conducting and the right hand section is cut ofi.

Six coincidence amplifiers,Vntl1rough Vis. are provided, one of which is associated with each of the trigger circuits 34 through 39. Each of these amplifiers is a pentode having its cathode connected lto ground through resistors 45 and its screen grid connected to the-high potential end of resistor 45 to place the properpositive potential thereon. The control grids of all the ampliilers are connected together and, by means of lead 41, to the control grid of V1, whereby the received coded signal is applied to the grids of these amplifiers at the same time that it is' applied to V1. Each of the coincidence amplifiers is biased to an inoperative condition by the application of a fixed negative potential to the suppressor grid; this potential is obtained from the drop across resistor 44. In order to cause the coincidence ampliers to become operative at the proper times,

vprovision is made for applying the 100 microsecond gating pulses produced by trigger circuits 34 through 39 to the suppressor grids of the corresponding amplifiers. This is accomplished by coupling the suppressor grid of each amplifier to the anode of the left hand section of the tube in the associated trigger circuit by means of condenser 48 through 53. Application of the positive gating pulse to the suppressor grid overcomes the negative bias on the grid and renders the amplier operative' for the duration of the pulse. Therefore, beginning 50 microseconds after the synchronizing pulse, coincidence amplifiers V1: through Via. are successively rendered operative for 100 microsecond intervals.

The decoder circuit described'is designed to energize six control circuits which are represented in Fig. 3 by relays #1 through #6. The contacts of these relays may -be connected in the control circuits so that closing the contacts energizes the circuits. The output of each of the coincidence amplifiers is rectified and the resulting direct voltage used to control the current in the relay coil. In the circuit of relay #1, for example, the output of Vn is applied through condenser 54 to the diode rectiiier in the left diiierentiating circuit comprising condenser 4I and resistors 42 and 43 and is applied to the control grid of the left hand section of V1. 'I'his causes trigger circuit 34 to rapidly change from grid of the left hand section of Vn through lter elements 56 and 51 causing the grid potential to be raised. A delay bias is applied to the diode by means of the voltage Adrop across resistor 53 so that no rectification is obtained luntil the sig- I nal applied to the diode exceeds the voltage across this resistor, thus preventing operation of the relay by noise or other extraneous signals. The negative potential drop across resistor B9 is also applied to the grid of the left hand section of Vu, thus reducing the current through the vcoil of relay #1 below its thresholdvalue in the absence of a signal. However, when control pulses appear in the output of Vn, the resulting rectiiled voltage applied to the grid ot the triode overcomes the negative bias and raises the plate current to a value suiilcient to operate relay #1.

'time interval, means responsive to said synchronizing pulsei for keying said oscillator, means The construction and operation oi' the remainingI relay circuits is the same as for relay #1.

In order for any one of the relays to be energized, it is necessary that in its associated coincidence amplier a control pulse be applied to the control grid during the time that a gating pulse is applied to its suppressor grid. For example, in the case of the coded signal shown in Fig. 2m) control pulses occur fat intervals of 200, 300 and 500 microseconds after the syncronizing pulse. It is also seen from Rig. 2 that trigger circuits 35, l0 and 3l respectively are producing gating pulses at these times. Therefore, associated coincidence ampliilers V14, Vis and Vr: will be operative at the timesnof occurrence of the ilrst, second and third cbntrol pulses respectively y and associated relays #2, #3 and #5 will beenergized.

What I claim is:

l. A decoding circuit for analyzing a coded sigi nal consisting of a sychronizing pulse and one cr more control pulses occurring at predetermined intervals of ytime after said synchronizing pulse, said decoding circuit comprising means for generating a series of pulses spaced at equal intery vais oi' time and beginning a xed interval of time after said synchronizing pulse, a plurality o! trigger circuits connected in cascade, said circuits being of the type having two conditions oi' stability, ilrst means iorvtriggering said circuits from one condition of stability to the other condition of stability and second means for triggering said circuits from said other condition of stability back to said one condition of stability whereby each circuit produces a pulse the duration of which is determined by the time interval between the operation of said 4ilrst and second means, said rst means comprising means for applying said synchronizing pulse to the ilrst trigger circuit and means utilizing the trailing edge ot the pulse produced by each trigger circuit to trigger the next succeedingV trigger circuit. said second means comprising means for applying said series of pulses to each of said trigger circuits. a plurality of coincidence circuits one of which is connected to each ofthe said trigger circuits in said cascade excluding the iirst, a plurality of control circuits one ot which is connected to each oi! said-coincidence circuits, and means tor applying the coded signal to each of said., coincidence circuits whereby those control circuits are energized that are connected to coincidence circuits in which a pulse produced by said trigger' circuits` and a control pulse from said coded' signal occur at the same time.

2. Adecodlng circuit for analyzing a coded sigi'or deriving from the output wave of said oscillator a series ot sharp negative pulses separated by said time interval and beginning a. length of time after said synchronizing pulse equal to one-half said time interval, a plurality oi' trigger circuits, each trigger circuit comprising a first and a second vacuum tube, each tube having an anode, a control grid 'and a cathode, means coupling the anode of each tube in said trigger circuits to the grid of its associated tube whereby each trigger circuit has a iirst condition of stability in which the first tube is conductive and the second tube non-conductive and a second condition oi stability in which the ilrst tube is non-conductive and the second tube is conductive, means connecting said trigger circuits in cascade with thegrid of the first tube of each trigger circuit coupled through a diierentiating circuit to the anode of the ilrst tube in the preceding trigger circuit. means for applying and synchronizing pulse to the grid oi' the ilrst tube oi' the first trigger circuit in said cascade and means for applying said series of negative pulses to the grid of the second tube in each trigger circuit of said cascade whereby the occurrence of said synchronizing pulse causes the trigger circuits of said cascade to operate in succession to produce a series of pulses with the length of the pulse produced by the ilrst trigger circuit being equal to one-half said time interval and the lengths of the pulses produced by the succeeding trigger circuits being equal to said time interval, a plurality of coincidence circuits. means for applying the pulse produced by each trigger circuit in said cascade excluding the first to one of said coincidence circuits whereby said coincidence circuit is rendered operative for the duration of said pulse, means for applying said Vcoded signal to each of said coincidence circuits,

and a control circuit connected to each of said coincidence circuits whereby those control circuits are actuated that are connected to a coincidence circuit to which a pulse from its associated trigger circuit and a pulse of the coded signal are applied at the same time.

` MAX E. SALLACH. REFERENCES crran y The i'ollowing references are of record in the ille of'this patent: u

.UNITED STATES PATENTS Date Number Name 2,099,065 Holden Nov. 16, 1937 2,272,070 Reeves Bieb. 8, 1942 2,381,920 Miller A--- Aug. 14, 1945 2,400,574 v Reav May 21, 1948 2,403,561 Smith July 9, 1946 2,409,229 Smith Oct. 15, 1946 

